Electrical connectors, method and apparatus



Dec. 10,1957

G. A. FULLER ETAL ELECTRICAL CONNECTORS, METHOD AND APPARATUS Fig-ZFiled Jan. 5, 1954 INVENTOR. GLENWOOD ARTHUR FULLER ROBERT ULLMAN BY m,hm phi/n4 United States Patent ELECTRICAL CONNECT QRS, METHOD ANDAPPARATUS Glenwood Arthur Fuller, Elizabethtown, and Robert Ullman,Harrisburg, Pa., assignors to AMP Incorporated, a corporation of NewJersey Application January 5, H54, Serial No. 402,248

6 Claims. (Cl. 339-276) This invention relates to electrical connectionsand methods of making them and apparatus for use therewith, and moreparticularly to the type of connections which are pressure-forged ontoelectrical conductors (commonly referred to as crimped).

More particularly the invention relates to electrical connections inwhich the connector is crimped onto an electrical conductor by theconverging pressure of circumferentially spaced indenting dies.

This invention, embodied in the above described type of crimp,contemplates the use of converging indenters of such width and numberthat the metal between them is dragged down with the adjoiningindentations and cannot make a fold projecting beyond the circumferenceof the barrel before indenting. In general, from five to ten indentersmay be used and six to eight are better. Eight is most advantageous.This multiple crimp has advantages over the old conventional type crimpswhere only two opposing dies compress the electrical connector onto anelectrical conductor or where there are more than two converging diesbut with said dies being spaced so that each makes a more or lessindependent indentation or pushes out a fold between adjacent indents.

A further important feature of invention embodied in the hereindescribed crimp is the skewed positioning of elongated indents and ofthe indenting edges of the dies which make them. The skewed crimp isespecially advantageous in crimping a plug type electrical connectoronto an electrical conductor. Generally, in this type of use the crimpedportion must not extend beyond the geometric surface of the plug, as itmight mechanically prevent the plug from being fully inserted into thereceiving member or electrically short circuit to nearby parts. Thisinvention makes it feasible to confine all parts of the crimp within thegeometric surface of the plug (i. e. extending the form of adjacentareas across the area of the crimp).

An importantadvantage of this skewed crimp is that opposite ends of eachindenting edge engage the barrel along chords which are respectively onopposite sides of a diameter., Thus, the indenters do not merely pushdown an area of the barrel, bending it inward, but exert a smearing ortrowelling effect forcing the metal against and into the wire by plasticflow. Moreover, because 0pposite ends of the die edge engage oppositesides of the barrel at longitudinally spaced positions they exert atwisting or wringing action on the barrel which tends to wrap it moretightly on the wire by a tensile action. Along each indent the metal isthus under tensile stress at the same time that it is subjected to thecompressive action of the indenters and this combined stress produces aunique action.

The skewed crimp in this invention affords relatively great contact areabetween the electrical connector and electrical conductor, andrelatively high pull out strength; ofiers great resistance to corrosionwhich keeps contact resistance low even in salt spray; distributes thepressure more evenly over the crimped portion, putting less strain "iceon the electrical conductor and thus resulting in less chance of failurein the conductor and also giving more consistent tensile properties.Even hard brass may be crimped without cracking, because of thegenerally circular shape of the crimped section free from acute bends.

Other objects and important features of the invention, will appear inthe following description and claims.

Although in the accompanying drawings we have shown a preferredembodiment of our invention and have described the same and variousmodifications thereof in this specification, it is to be understood thatthese are not intended to be either exhaustive or limiting of theinvention, but, on the contrary, are chosen for the purposes ofillustrating the invention in order that others skilled in the art mayso fully understand the invention, its principles and the applicationthereof, that they may embody it and adapt it in numerous forms, each asmay be best suited to the requirements of its particular use.

In the accompanying drawings a preferred embodiment of the presentinvention is set forth.

In these drawings:

Figure 1 shows a plug type connector before crimping.

Figure 2 shows an insulated conductor with the insulation stripped fromits end and the conductor end folded back ready for insertion into theopen end of the barrel of the terminal shown in Figure 1.

Figure 3 shows the terminal after it has been crimped onto the conductorin accordance with my invention.

Figure 4 shows a straight edge crimping die in a position just removedfrom a fully crimped plug barrel crimped by a plurality of suchindenting dies. Only one die is shown for the sake of clarity but eightsuch dies converge simultaneously to make the crimp shown.

Figure 5 is a view like that of Figure 4 but showing a crimping die witha concave edge.

Figure 6 shows an enlarged cross section taken on line 66 of Figure 3.The location of the eight crimping dies in nearly converged positionsare shown in Figure 6.

Figure 7 is a section on line 77 of Figure 3 on the same scale as Figure3.

Figure 1 shows a plug barrel 21 formed from a flat piece of connectormetal, e. g., quarter or half hard electrical copper or brass, with abutt seam 22 along its entire length. This seam has a tendency todistort and become misshapen when one of the ordinary crimps is used. Asshown in Figure 2, the insulation is stripped from the end of the wireand the bared wire 25 is folded back over the insulation 26 preparatoryto inserting it into the open end 23 of plug barrel 21. Thus a smallconductor may be crimped in a much larger plug connector withoutpre-shaping the plug connector. With larger wires the bated end of theconductor may be in serted coaxially without bending.

Figure 3 shows the completed connection with the skewed indentations 30.These indentations in the example shown are equally spaced, of about theproportions shown and the axis of each indent (i. e. the center linealong the bottom of each indentation) makes an angle of approximatelytwenty-five degrees (25") with an axial plane of the barrel. Thisarrangement of indentations assures that the seam of the plug barrelwill be crossed by at least one indentation without need for any specialorientation of the plug in the dies. This advantage may be attained withcurved or angular or even X indentations as well as sloping straightlines.

The length of the indenting edges of the dies and their overlap relativeto an axial plane of the barrel is such as to assure that at least onesuch die will extend substantially to both sides of the seam and engagethe barrel on both sides of the seam.

Figure 6 is a cross sectional view of the crimp 66 ofFigure 3. Here itis seen that seam 22 lies fiat in a closed condition. The folded overportion of the conductor is shown at 25 and the electrical contact withthe connector is shown at 35. The conductor insulation and conductorwire, along with the folded .over portion, are tightly embraced andenclosed by connector 34. The. indentations are formed by dies 33 thelocation of which are shown by dashed lines. Eight dies were used toform the eight indentations so that a nearly round crimp could beobtained but this invention is not restricted to eight dies; although wehave found significant advantage in the eight indent crimps as comparedeven with six or ten.

The fact that this crimp makes a high quality connection withoutsubstantial enlargement or any diameter is regarded as most significantfor some uses. In this skewed crimp, all eight indentations 30 areplaced so that their longitudinal axes 29 form approximately atwenty-five (25 degree angle with an axial plane of the wire. This anglemay be varied, but if too nearly parallel to the conductor axis 23 itwill assume the inferior character of a radial indentation; and if attoo great an angle it will become a mere cross-crimp, losing the specialadvantage of the wringing action. In order to avoid dragging the seamopen, it should always be crossed by at least one indentation whichengages the ferrule firmly on both sides of the seam regardless of itsorientation in the dies. Therefore, with a longer and/ or widerindentation a smaller angle may be used and still insure that the seamwill be held closed.

A preferred embodiment of this invention is to have the indentationsconform to the curve of the plug barrel surface. This is shown in Figure5 in which a concave edge 42 conforms to the surface of the plug barrelwhen initially contacted by the die. Such concavity is not circular butan arc of an ellipse because the plane of the indenter edge of the dieintersects the plug barrel at an oblique angle. This has the advantageover the flat indentation of engaging the plug barrel from the first onboth sides as well asat the center, thereby preventing spreading of thebarrel or other distortion which might allow the seam to open. Theentire curved die edge comes into contact with the plug barrel from thefirst moment of impact while a straight die edge would be touching onlya point of tangency or a very small area of contact. Even with thestraight edged die, however, it will engage opposite sides to give thewringing action, to an increasing extent as the indentation progresses.

Figure 7 shows how the ends of the die edge push the metal of the plugbarrel across the wire, giving better contact and twisting or wringingthe plug barrel around the conductor wire. This wringing effect is alsoshown in Figure 3 where the seam is twisted in the crimped section,binding it tightly together.

In the skew crimp, each indentation covers a larger arc of theelectrical conductor circumference than does each indentation of formerparallel radial indenters and therefore provides a greater transverseedge 31 to retard any longitudinal movement of the electrical conductorin relation to the plug terminal.

A straight die edge used in the skew crimp of this invention has anotheradvantage over known crimps. It produces an indent with maximum pressureon the conductor at the center and progressively less pressure towardthe end of the indent. This is due to the straight edge skew die makingits deepest impression on the barrel at the center of the barrel. Thisgradual decrease of pressure puts less strain on the wire, eliminatessharp shoulders that weaken the wire, especially when the wire issubject to vibration or tensile stress.

Although this crimp may be used on any type electrical connector andeven for mechanical connections, its advantages are especiallysignificant in terminals such as plug type terminals shown in thedrawings.

We claim:

1. In an electrical connection of the type adapted to embrace anelectric wire comprising a tubular metal barrel, a longitudinal seamalong the outer surface of the barrel and a plurality of crimpedindentations impressed in the outer surface of the barrel and extendingaround the barrel forming a constricted band, at least one of saidindentations being set at an oblique angle with respect to thelongitudinal seam.

2. An electrical connector of the type adapted to embrace an electricwire comprising: a tubular metal barrel, a longitudinal seam along theouter surface of the barrel, and a plurality of crimped indentationsimpressed in the outer surface of the barrel and extending around thebarrel forming a constricted band; each indentation being set at anoblique angle with respect to the longitudinal seam, and theindentations being of sufficient length and number that each indentationoverlaps each of the respective indentations on either side of it.

3. The connector of claim 2 wherein the indentations comprisetrough-like portions, said portions having straight bottom portions.

4. The connector of claim 2 wherein the indentations comprisetrough-like portions, said portions having curved bottom portions.

5. In an electrical connection the combination comprising an electricalconductor having an insulated body portion and a coextensive uninsulatedend portion, said uninsulated end portion being folded back over theadjacent insulated portion, an electrical connector surrounding theuninsulated end portion and the coextending insulated body portion, saidconnector having a seam which extends longitudinally of the electricalconductor, said connector having indentations impressed on the outersurface thereof securing the connector on the conductor, and saidindentations being generally similar and extending helically so as toform oblique angles with the longitudinal axis of the connector.

6. The method of crimping the bare end of an electric wire within aconnector having a seam running longitudinally of the wire whichincludes inserting the bare end of the wire into the connector andcrimping the connector onto the Wire with a plurality of indentations sothat each indentation is at an angle to the longitudinal axis of thewire and at least one of the indentations forms an oblique angle withand crosses the seam.

References Cited in the file of this patent UNITED STATES PATENTS1,376,735 Stalhane May 3, 1921 2,008,227 Reilly July 16, 1935 2,143,564Lybarger Jan. 10, 1939 2,210,804 Ely Aug. 6, 1940 2,276,140 Andren Mar.10, 1942 2,280,351. Penfold Apr. 21, 1942 2,346,831 'Drury Apr. 18, 19442,467,012 Deuscle Apr. 12, 1949 2,480,280 'Bergan Aug. 30, 19492,639,754 Macy May 26, 1953 FOREIGN PATENTS 125,077 Great Britain Jan.8, 1920 463,781 Great Britain Apr. 6, 1937

